The invention relates to a method for operating a clutch release system of a vehicle with an electrically actuable clutch release mechanism, which includes a sensor for detecting a position of a release plunger of the clutch release mechanism and a control device, which controls a release plunger as a function of a detected position of a clutch actuation device. A further sensor detects the position of the clutch actuation device.
The invention furthermore relates to a clutch release system with an electrically actuable clutch release mechanism, which includes a sensor for detecting a position of a release plunger of the clutch release mechanism and a control device, which controls a release plunger as a function of a detected position of a clutch actuation device. A further sensor detects a position of a clutch actuation device.
A drivetrain of a vehicle usually has a clutch which is suitable for interrupting the drivetrain of the vehicle. The interruption of the drivetrain is required, for example, in the event of a gear change in a transmission arranged in the drivetrain.
Ordinarily, the clutch includes a clutch actuator, which in turn normally has a power part and a control part. The power part performs the task of providing the releasing force using a pressurized medium, for example compressed air from a tank. The power part includes a release plunger and a valve control mechanism, which may be in the form of a solenoid valve control mechanism, for example.
During the actuation of the clutch, a clutch disk between a pressure plate and a flywheel is lifted, whereby a transmission of torque from the flywheel to a driver disk, which is connected in a manner fixed against rotation to the pressure plate, is interrupted. The release bearing driven during the lifting process is in this case caused to disengage by performing a pushing movement, in the case of a pushing design of the clutch, and a pulling movement, in the case of a pulling design of the clutch, in order to eliminate the contact-pressure forces which are usually generated by plate springs and to open the clutch. In the case of an eccentric arrangement of the clutch release mechanism, it is possible to realize force transmission from the clutch release mechanism or clutch actuator to the release bearing via a lever.
The control part of the clutch release mechanism includes a clutch transducer, which measures a pedal travel, wherein the measured travel is predetermined proportionally, as a hydraulic or electrical variable, to the intensifying power part, for example a cylinder, as a setpoint variable. This setpoint variable can then still be corrected, in particular in the case of an electrical signal transmission. In the case of a hydraulic control circuit of the clutch, leak compensation is possible by virtue of a valve-controlled continuing flow of oil from a tank. Electrically controlled clutch actuators or clutch release mechanisms are predominantly driven by transmission electronics of an automatic transmission, wherein electrical clutch actuators have the advantage that the control circuit does not need to be deaerated and is not sensitive to leaks. Furthermore, there are motor-driven actuators, but these are not sufficiently robust for commercial vehicle applications and cannot perform shifting operations at high power or quickly enough.
Conventionally, a clutch which is used has at least one wearing part, for example a clutch disk or a clutch lining, which is worn away when the clutch is shifted. In this case, the material thickness of the wearing part decreases continuously, for which reason the shift point of the clutch, i.e. the point at which the wearing part enables a first force transmission via the clutch, is moved.
In order to release the clutch, there are hydraulic control circuits, but these do not have the option of wear adaptation and also do not enable any software-based learning of a characteristic for the clutch release.
In order to solve this problem, it is known to design the clutch to be self-adjustable with the aid of an elastic element, for example a spring, which prestresses the clutch disk. The wear adaptation then takes place automatically via the prestressed mechanism.
Furthermore, there are fully electronic transmission shift mechanisms which can also have integrated control circuits for clutch release and have a very complex design. The installation space available for an electrical control circuit in the vicinity of the drivetrain is subjected to a high temperature of approximately 110° C., for which reason more stringent requirements need to be placed on all of the constructed electronics in this region. A clutch release mechanism for such a transmission shift mechanism which has self-adjusting wear adaptation is known from DE 10 2006 037 958 A1, for example.
The invention is based on the object of providing a method for operating a clutch release system, with the aid of which the design of the operated clutch system can be simplified while retaining the same functionality.
In accordance with the invention, a characteristic function F, which describes a relationship between the position of the clutch actuation device and the position of the release plunger, is taken into consideration during the actuation of the clutch release system in order to achieve constant clutch release, despite progressive wear on the clutch release system, in the case of a defined position of the clutch actuation device. By matching the clutch release system to the progressive wear, the outwardly visible properties of the clutch release system can be kept constant over the life of the wearing parts used and the operational convenience can be increased. At the same time, the wear adaptation ensures operation of the clutch release system which is gentle on the materials since longer-lasting abrasion of the wearing part can be avoided. No additional mechanism is required for the adaptation itself since the adaptation takes place with the aid of the characteristic function F.
It is particularly preferred that the characteristic function F is stored in a random-access memory arranged in the clutch release system.
Provision is preferably made for, during the actuation of the clutch release system, an updated characteristic function Fact to be determined by the control device. The updated characteristic function Fact describes an actual relationship between the position of the clutch actuation device and the position of the release plunger. The stored characteristic function F is replaced by the updated characteristic function Fact after the actuation of the clutch release system in order to provide an actual characteristic function F during the next actuation of the clutch release system. In this way, continuous wear adaptation of the clutch release system with each shifting operation is achieved.
In particular, provision can be made for the clutch slip during the actuation of the clutch release system to be taken into consideration for determining the updated characteristic function Fact via a connection to a CAN bus.
Usefully, provision can be made for a warning signal to be output if a permissible wear value stored in an electrical random-access memory is exceeded by a determined wear value. In this case, for example, the stored characteristic function F indicates that a permitted wear on a wearing part has been exceeded by a large no-load excursion L1′. The no-load excursion of the clutch release system increases in size as the wear on the wearing part increases, since the material thickness of the wearing part decreases. If the material of the wearing part has largely been eroded away, this can be detected by a measurement of the no-load excursion of the clutch release system, for example by virtue of a comparison with the original no-load excursion of the clutch release system L1 with an unused wearing part. The output of a warning signal in the event of a permitted wear on a wearing part, for example a clutch disk, being exceeded serves to safeguard the operational readiness of the vehicle since a surprising failure of the clutch release system owing to a completely worn clutch disk can be avoided.
Furthermore, provision can be made for the vehicle to be taken out of operation if the stored characteristic function F indicates that a permissible wear on a wearing part has been exceeded by a large no-load excursion L1′. Taking the vehicle out of operation serves to protect sensitive vehicle components which could be damaged in the case of complete wear of a wearing part, for example a clutch disk. The permissible wear, i.e. the thickness of the material eroded away by friction, is in this case determined by a minimum stability, required for safety reasons, of the clutch disk. This minimum stability represents the limit below which it is no longer possible to rule out a rupture.
Provision can also be made for the stored characteristic function F to be stored in the random-access memory in the factory prior to the first actuation of the clutch release system.
Alternatively, provision can be made for the stored characteristic function F to be determined during the first actuation of the clutch release system and to be stored in the random-access memory. The determination of the characteristic function F during the first actuation of the clutch release system enables simple manufacture of the clutch release mechanism with comparatively large tolerances and automatic adaptation of the clutch release mechanism to various clutch actuation devices, since any deviations from a desired response can be compensated for via the characteristic function F.
The clutch release system is developed by virtue of the fact that the control device is suitable for taking into consideration a characteristic function F, which describes a relationship between the position of the clutch actuation device and the position of the release plunger, during the actuation of the clutch release system in order to achieve constant clutch release, despite a progressive wear on the clutch release system, in the case of a defined position of the clutch actuation device.
In this way, the advantages and special features of the method according to the invention are also used in the context of a clutch release system. This also applies to the particularly preferred embodiments of the clutch release system according to the invention specified below.
This clutch release system is usefully developed such that the control device is suitable for determining, during the actuation of the clutch release system, an updated characteristic function Fact, which describes an actual relationship between the position of the clutch actuation device and the position of the release plunger, and that the control device is suitable for replacing the stored characteristic function F by the updated characteristic function Fact after the actuation of the clutch release system in order to provide an actual characteristic function F during the next actuation of the clutch release system.
Furthermore, provision can be made for the clutch release system to include a connection to a CAN bus. The connection to the CAN bus can be used for compensation with external vehicle parameters, for example a motor speed and a transmission speed, wherein the instantaneous clutch slip can be determined from the two mentioned vehicle parameters together with the actual transmission ratio.
Provision can be made for the control device to be suitable for outputting a warning signal if the stored characteristic function F indicates that a permitted wear on a wearing part has been exceeded by a large no-load excursion L1′.
Furthermore, provision can be made for the control device to be suitable for bringing the vehicle out of operation if the stored characteristic function F indicates that a permissible wear on a wearing part has been exceeded by a large no-load excursion L1′.
Preferably, provision can be made for the control device to be suitable for determining the characteristic function F during the first actuation of the clutch release system and storing said characteristic function in the random-access memory.
An electrically actuable clutch release mechanism can be developed by virtue of the fact that a control device for driving the valve device is arranged in the housing of the clutch release mechanism. The arrangement of the control device in the housing of the clutch release mechanism enables a modular design of the clutch release mechanism, with it merely being necessary to provide a media supply connection and a media discharge line for supplying the release plunger which moves the clutch release mechanism and a connection for detecting a clutch actuation desire. This has the advantage that even relatively small, relatively light vehicles which use primarily mechanical transmissions and clutches can make use of the advantages of an electrical clutch release mechanism, with no further changes to the vehicle being necessary. Furthermore, the clutch system can be configured with a learning capacity by virtue of the integrated control device.
Preferably, provision is made for the valve device to be coupled to a connection in order to be supplied with compressed air. The supply of compressed air to the clutch system as the shifting medium avoids damage to the friction lining of the clutch caused by a hydraulic fluid.
Usefully, provision can be made for a sensor for detecting a position of the release plunger of the clutch release mechanism with respect to the fixed housing to be arranged in the housing. By virtue of the detection of the position of the release plunger with respect to the fixed housing, it is possible for the clutch release mechanism itself to detect faulty operation of the clutch release mechanism.
Provision can be made for the valve device to include a 3/2-port directional control valve. The use of a 3/2-port directional control valve, which can be in the form of a solenoid valve, for example, makes it possible for the switching positions of the valve device which are necessary for operating the clutch release mechanism to be realized with the aid of a single valve. In this case, a first connection is coupled to a media supply, a second connection is coupled to a media discharge line and a third connection is coupled to a control area of the release plunger.
In this case, provision is preferably made for the valve device in the connecting line between the 3/2-port directional control valve and the control area to include a 2/2-port directional control valve in the form of a pressure maintenance valve. The pressure maintenance valve can be used to extend the life of the 3/2-port directional control valve driven in pulse-width-modulated fashion since no further switching operations are required during the pressure maintenance.
Alternatively, provision can be made for the valve device to include two 2/2-port directional control valves. The use of two 2/2-port directional control valves, which can be in the form of solenoid valves, for example, likewise makes it possible to realize all of the switching states of the valve device which are required for the clutch release mechanism, with it being possible for the 2/2-port directional control valves to be more robust than a single 3/2-port directional control valve.
Provision can be made for the control device to have a connection to a serial vehicle bus in order to output at least one signal for the clutch wear. A replacement of the clutch linings prior to failure of the clutch system is enabled via the signal for the clutch wear.
Furthermore, it is possible for the valve device to include a common media discharge line. A common media discharge line saves on installation space in the housing. The common media discharge line can in particular be in the form of a simple deaeration bore if compressed air is used as the medium.
Advantageously, provision can be made for a random-access memory to be arranged in the housing of the clutch release mechanism. The random-access memory is provided for storing a characteristic function F and an updated characteristic function Fact. In this case, the storage can also take place in the form of sets of parameters, from which a characteristic function can be determined or which are suitable for replacing the function of the characteristic function. By virtue of the arrangement of a random-access memory in the housing of the clutch release mechanism, it is possible to perform automatic wear adaptation of the clutch release mechanism in the case of progressive wear on the clutch.
Preferably, provision is made for a plug for electrical connections to be arranged on the housing. A plug provides a simple possible way of providing a standardized connection, as a result of which the integration of various clutch release mechanisms in one vehicle or one clutch release mechanism in various vehicles is facilitated.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.